Demonstrates consuming the SwiftNIO library through simple async/await methods

This code example is a simple TCP client built on SwiftNIO. SwiftNIO predates the concurrency features built into the Swift language, such as the async and await keywords. Although SwiftNIO is being retrofitted to support these language features, this work is not yet complete.¹

This example shows an interim approach. Specifically, it adds two async methods to Channel:

func asyncRead() async throws -> ByteBuffer?

func asyncWrite(_ buffer: ByteBuffer) async throws

asyncRead() is implemented by an AsyncThrowingStream. Backpressure is applied to throttle incoming data to keep the number of bytes buffered by the AsyncThrowingStream within a target range, specified by unconsumedBytesLowWatermark and unconsumedBytesHighWatermark.

The implementation of asyncWrite(buffer:) is trivial, since SwiftNIO already supports an async write API.

This example is a simple client that opens a TCP socket to a server, then reads lines from stdin (the keyboard), writes those lines to the socket, reads data from that socket, and prints that data to stdout. It can be run against the NIOEchoServer or NIOChatServer examples included in SwiftNIO (https://github.com/apple/swift-nio) or the NIOTLSServer example included in https://github.com/apple/swift-nio-ssl.

To run:

• Start the server of your choice
• Set the values of host, port, and useSSL
• From the terminal, swift run to start the client
• Ctrl+D to exit